On the big screen, Australian-born actress Margot Robbie may be best known for playing devil-may-care anti-heroes—like Suicide Squad member Harley Quinn and notorious figure skater Tonya Harding. But recently, a discussion of her role in Peter Rabbit proved that in real life, she’s making healthier choices. When asked whether it was hard to voice a character with a speech impediment, she revealed that she wears retainers in her mouth at night, which gives her a noticeable lisp.

“I actually have two retainers,” she explained, “one for my bottom teeth which is for grinding my teeth, and one for my top teeth which is just so my teeth don't move.”

Clearly Robbie is serious about protecting her dazzling smile. And she has good reasons for wearing both of those retainers. So first, let’s talk about retainers for teeth grinding.

Also called bruxism, teeth grinding affects around 10 percent of adults at one time or another, and is often associated with stress. If you wake up with headaches, sore teeth or irritated gums, or your sleeping partner complains of grinding noises at night, you may be suffering from nighttime teeth grinding without even being aware of it.

A type of retainer called an occlusal guard is frequently recommended to alleviate the symptoms of bruxism. Typically made of plastic, this appliance fits comfortably over your teeth and prevents them from being damaged when they rub against each other. In combination with stress reduction techniques and other conservative treatments, it’s often the best way to manage teeth grinding.

Orthodontic retainers are also well-established treatment devices. While appliances like braces or aligners cause teeth to move into better positions, retainers are designed to keep teeth from moving—helping them to stay in those positions. After active orthodontic treatment, a period of retention is needed to allow the bite to stabilize. Otherwise, the teeth can drift right back to their old locations, undoing the time and effort of orthodontic treatment.

So Robbie has the right idea there too. However, for those who don’t relish the idea of wearing a plastic appliance, it’s often possible to bond a wire retainer to the back surfaces of the teeth, where it’s invisible. No matter which kind you choose, wearing a retainer can help keep your smile looking great for many years to come.